1. Field of the Invention
The present invention relates generally to prosthetics. More particularly, the present invention relates to a socket of a prosthetic for receiving the stump of an amputee, and which includes a variable viscosity fluid.
2. Related Art
Many individuals have lost a limb for various reasons including war, accident, or disease. In most instances, these individuals are not only able to live relatively normal lives, but physically active lives as well. Often times, these individuals are aided in their everyday lives by a prosthetic limb. The objective of prosthesis is to provide an artificial limb that simulates the function and natural feel of the replaced limb.
With respect to prosthetic feet, the development of a functional and natural artificial foot has been limited only by material and imagination. Many designs have attempted to copy the anatomy of the foot or simulate its actions by replacing the bones and muscle with various mechanical components. Other designs have departed radically from mere anatomical copying or mechanical simulation by replacing the entire foot with an energy storage element, such as a spring. As the user steps onto the foot, the user""s weight compresses the spring. As the user moves forward, the user""s weight comes off the foot and the energy stored in the spring is used to propel the user forward. Examples of such energy storing, spring-like feet include U.S. Pat. Nos. 5,037,444; 4,547,913; 5,181,932 and 5,976,191. The prosthetic feet typically include spring-like members that are typically flexible and resilient. In order to provide a natural feel and cushion of a natural foot, the members must be flexible and deflect under the user""s weight.
Such prosthetic feet typically include a socket for receiving the user""s stump. The prosthetic foot or spring can be attached to the socket, attached to pylon that is attached to the socket, or the like. It is desirable to provide a socket that is comfortable for transferring forces from the prosthetic, such as the prosthetic foot, to the user""s stump. In addition, is it desirable to provide a socket that accommodates the swelling and/or contracting of the user""s stump.
It has been recognized that it would be advantageous to develop a prosthetic or socket thereof that is comfortable, or that provides a comfortable fit with the user""s stump, and which is comfortable during use. In addition, it has been recognized that it would be advantageous to develop a prosthetic or socket thereof that accommodates the swelling and/or contraction of a user""s stump.
The invention provides a socket device to attach a prosthetic to a stump of an amputee. The socket device can include an outer shell coupled to the prosthetic and has a cavity to receive the stump of the amputee. An internal liner is disposed in the cavity of the outer shell, and is disposed between the stump of the amputee and an internal surface of the cavity. The internal liner advantageously includes a variable viscosity fluid to variably transfer energy between the stump of the amputee and the outer shell in response to changes in load applied to the liner. In addition, the variable viscosity fluid of the internal liner can accommodate the swelling and/or contracting of the user""s stump.
In accordance with a more detailed aspect of the present invention, the internal liner can include a bladder having a hollow with the variable viscosity fluid disposed therein. In addition the internal liner can further include a layer of cushion material.
In accordance with another more detailed aspect of the present invention, the variable viscosity fluid can include a shear stiffening material that increases in viscosity with an increase in a load factor applied to the shear stiffening material. The load factor can include a load, a load rate, a strain, or a strain rate.
In accordance with another more detailed aspect of the present invention, the variable viscosity fluid can include a magneto rheologic fluid responsive to a magnetic field. In addition, the variable viscosity fluid can include an electro rheologic fluid responsive to an electric field.
In accordance with a more detailed aspect of the present invention, a transducer can be coupled to the prosthetic or socket to sense strain. A power source can be coupled to the transducer. Control electronics can be coupled to the transducer and the variable viscosity fluid to apply the electric field in response to the strain sensed by the transducer.
In accordance with another more detailed aspect of the present invention, an orifice can be provided through which the variable viscosity fluid flows, or is forced, during use.
In accordance with another more detailed aspect of the present invention, the internal liner and variable viscosity fluid can be flexible and conform to fit the contours of the stump of the user.
In accordance with another more detailed aspect of the present invention, the internal liner can further include a plurality of flexible compartments, at least one of the compartments containing the variable viscosity fluid.
A method for varying a stiffness of a socket of a prosthetic and conforming the socket to a stump of an amputee includes inserting the stump of an amputee into a socket of a prosthetic. The socket includes a shell shaped and sized to receive the stump, and a variable viscosity fluid disposed between the shell and the stump of the amputee. The shape of the liner and the variable viscosity fluid are changed to match contours of the stump of the amputee. The viscosity of the fluid is varied in response to loading on the shell or the prosthetic foot, so that the stiffness of the variable viscosity fluid varies, including increasing viscosity during increased loading for a stiffer feel during the increased loading, and decreasing viscosity during decreased loading for a softer feel during the decreased loading. In addition, the shape of the liner and the viscosity of the fluid can accommodate the swelling and/or contraction of the user""s stump.
Additional features and advantages of the invention will be apparent from the detailed description which follows, taken in conjunction with the accompanying drawings, which together illustrate, by way of example, features of the invention.